Take a moment to consider a system in which inverter units (i.e. power electronics devices) are provided with a communication function and autonomous cooperative control is applied between the power electronics devices to provide the flexibility of installation locations for the power electronics devices while enabling a capacity increase of fully-automatic at the time of expansion and maintenance of a power electronics device.
At this time, for example, in a case where multiple power electronics devices are activated in parallel to increase an output of power, it is necessary to consider a power source phasing function. An object of the power source phasing is to prevent an occurrence of cross current (e.g. reactive current caused by a difference of electromotive force, synchronization cross current caused by a phase difference of electromotive force and harmonic cross current caused by a waveform difference of electromotive force) in an output on the alternating-current side. In this case, however, it is essential to determine the subject of control, namely a master device (or simply “master”) in the multiple power electronics devices. A power electronics device controlled by the master corresponds to a slave device (or simply “slave”).
In the related art, there is disclosed a method of operating multiple power electronics devices in parallel by optical communication and implementing a power source phasing without using a current-limiting reactor. Also, there is disclosed a method of dynamically coping with power distribution between the multiple power electronics devices.
However, when multiple power electronics devices are installed and operated, a problem is that manual management becomes complicated as the scale increases. For example, regarding determination of a master/slave relationship between multiple power electronics devices, it is presumably applied to a small number of units in the related art. As in a massive power source phasing function, in order to activate multiple power electronics devices as master candidates in parallel, it is necessary to determine a master/slave relationship in multiple layers. Although a structure between units varies depending on the use (e.g. power distribution or power source phasing) of power electronics devices, a supposition is fixed in the related art.
As described above, the related art does not solve a problem of manual management becoming complicated as the scale increases when multiple power electronics devices are installed and operated. Also, although a structure between units varies every use of power electronics devices, the supposition in the related art provides a framework of fixed setting.